This is the view downstream from the footbridge across the former ship channel at Cascade Locks. The "toe" of the Bonneville Landslide, if you want to be picky, is really the outer perimeter of the whole debris lobe. However, I've been tending to think of it as the point where it's closest to the south shore. I'm pretty sure there's no narrower portion of the river downstream from here, and suspect it's quite a ways upstream before you'd find a similar neck, so this is indeed a good spot for a bridge. The well-known Pacific Crest Trail crosses the river at this point.